YoungSeon.Ahn

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1 minute read

Environment

  • typescript v5.8.3
  • yarn workspace

The Symptom

  1. Build a monorepo using yarn workspace
  2. Set up tsconfig at the workspace root
  3. Extend the workspace root’s tsconfig in a sub-package
  4. The global type defined at the workspace root is not recognized in the sub-package!

The Cause

This happens because both the workspace root’s tsconfig and the sub-package’s tsconfig had their own include settings.

The include setting is not extended. It is only overridden.

That is why the global type set at the workspace root was not applied to the sub-package.

The Solution

Set include only in the sub-package, as shown below.

{
  "extends": "../../tsconfig.json", // the workspace root's tsconfig
  "files": [],
  "include": ["src", "../../types/**.d.ts"] // the global type is defined at this path
}

How to Debug TypeScript Configuration

There is a way to check how tsconfig is configured in the current directory.

tsc --showConfig

Using the command above, you can check the TypeScript configuration resolved for the current directory. The output looks like the following.

# Output of tsc --showConfig
{
    "compilerOptions": {
        "tsBuildInfoFile": "../../node_modules/.tmp/tsconfig.app.tsbuildinfo",
        "target": "es2020",
        "useDefineForClassFields": true,
        "lib": [
            "es2020",
            "dom",
            "dom.iterable"
        ],
        "module": "esnext",
        "skipLibCheck": true,
        "composite": true,
        "emitDeclarationOnly": true,
        "moduleResolution": "bundler",
        "allowImportingTsExtensions": true,
        "isolatedModules": true,
        "moduleDetection": "force",
        "noEmit": true,
        "jsx": "react-jsx",
        "strict": true,
        "noUnusedLocals": true,
        "noUnusedParameters": true,
        "noFallthroughCasesInSwitch": true,
        "noUncheckedSideEffectImports": true,
        "allowSyntheticDefaultImports": true,
        "resolvePackageJsonExports": true,
        "resolvePackageJsonImports": true,
        "resolveJsonModule": true,
        "declaration": true,
        "preserveConstEnums": true,
        "incremental": true,
        "noImplicitAny": true,
        "noImplicitThis": true,
        "strictNullChecks": true,
        "strictFunctionTypes": true,
        "strictBindCallApply": true,
        "strictPropertyInitialization": true,
        "strictBuiltinIteratorReturn": true,
        "alwaysStrict": true,
        "useUnknownInCatchVariables": true
    },
    "files": [
        "./src/Header.tsx",
        "./src/Title.tsx",
        "./src/main.tsx",
        "./src/vite-env.d.ts",
        "../../types/global.d.ts"
    ],
    "include": [
        "src",
        "../../types/**.d.ts"
    ]
}

EOD

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